FULL COURT PRESS

ZF Sachs AG (Schweinfurt, Germany) replaced a press line for gearbox components used by commercial vehicles in order to raise output. In addition to the new line from Schuler AG (Goeppingen, Germany), an existing deep drawing press was also modernized by Schuler. Thanks to this extensive press retrofit, performance has doubled and the line can be used much more flexibly.

ZF Sachs has been manufacturing casing covers for commercial vehicles on its line in Schweinfurt since the 1990s. Due to strong demand and high capacity utilization, output on the existing line had long been insufficient. It was replaced by a new press line consisting of three hydraulic Schuler presses.

In a second step, the existing deep drawing press was modernized by means of a retrofit. With regard to the current high demand and full utilization of production capacity, Bernd Burger, responsible for the project at ZF Sachs, says, ?As with the press line, we chose an experienced partner because we could be sure that the line would be up and running within the shortest possible time.?

HIGH OUTPUT, MUCH FLEXIBILITY

The technological basis of the new production line is a hydraulic press line comprised of a lead-off press with a force of 1,800 U.S. tons (1,600 metric tons) and two presses of the SH line, each with 700 U.S. tons (630 metric tons) of press force. The three presses are linked by an electronic three-axis transfer system.

Together with the newly equipped deep drawing press, the plant can now use the line in two different operating modes. Each SH press is equipped with three working cylinders that can be selected to adapt to the required forming force, resulting in an increase in slide speed that, in turn, increases the number of parts produced.

As an automated 4-machine line, the blanks are fed to the deep drawing press by feeders and transfer and subsequently run through the entire line. The company was able to double output in this operating mode.

Additional flexibility is guaranteed by the possibility of operation as an automated 3-machine line, in which blanks or formed parts are fed directly into the second press. The deep drawing press can also be operated as a stand-alone press and can produce other parts via manual operation against the feed direction.

To optimize the efficiency of each SH press, the impact shock dampening unit is mounted next to the press bed. Additional bed surface is available between the dampeners for special applications.

Because the adjustable stop spindles are designed to suit the full press force, they guarantee superior repeatability of the slide position in bottom dead center (BDC). This means fixed stops on the die are no longer necessary, which improves process stability and reduces the cost of dies. This impact shock dampening also protects the press and the die, and reduces noise emission.

To ensure long service life for the die, each SH press has an eight-way flat guiding design that uses high quality bronze inserts and wear-resistant guide strips. This system enables worn guide strips to be adjusted or exchanged via cams in any direction.

A parallelism control system maintains the absorption of high off-center forces to improve process stability, increase die service life, and improve part quality and output. In designing the press, parallelism is controlled by either using two main cylinders or integrating four impact shock dampening cylinders.

These new presses pay special attention to user-friendly maintenance. All components are arranged for easy accessibility, and all sub-assemblies can be easily and quickly installed or removed so that the presses can be efficiently and cost-effectively maintained or overhauled/rebuilt.

An oil tank is located on the crown of each SH hydraulic press. The capacity-controlled axial piston pumps are mounted inside the tank. Inside the presses, a direct drive supplies the entire system with hydraulic oil without a pressure accumulator so that the system pressure correlates directly to the pressure requirement of the die. Block hydraulics are used for all hydraulic functions to ensure reliability and ease of maintenance and assembly.

The two-part, movable hydraulic bed cushion ensures part quality and guarantees total process flexibility. These drawing cushions use multipoint control to absorb off-center loading and allow the dies to be located in any position on the bed. Controlled blankholder forces optimize material flow control over the entire drawing process.

Following all of this modernization, the company is producing a far greater range of parts on the line than previously possible.

INCREASING EXISTING ECONOMIC EFFICIENCY

The successful retrofit of the deep drawing press plays a decisive role with regard to economic aspects. Schuler overhauled the entire hydraulics of the 800 ton press and equipped it with completely new electrical and control systems. The press was also equipped with a newly-developed modular electronic three-axis transfer. Thanks to its ability to flexibly adapt to a wide variety of applications, this transfer is ideally suited for use by ZF Sachs.

The direct drive, for example, enables the space-saving positioning of the coil magazine and blank feeder directly at the entry side of the press. Due to the extreme rigidity of the new transfer, only one clamping box is required. This means that the deep drawing press is accessible for manual operation on the exit side.

This retrofit is a perfect example of how users can gain maximum benefit from their existing machine situation. Falk Plaschke, Project Manager Service and Sales at Schuler, explains the benefits of targeted retrofitting as follows: ?Considering the high price of steel at present, the general rule is: if the mechanics of the basic frame are adequate, a retrofit can raise the output of existing lines in such a way that they fit seamlessly into a modern manufacturing environment.?

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ZF Sachs AG, Ernst-Sachs-Straße 62, 97424 Schweinfurt, Germany, +49 9721 98-0, Fax: +49 9721 98-2290, www.zf.com.

Schuler AG, Bahnhofstr. 41, 73033 Göppingen, Germany, + 49 (0) 71 61 66-0, Fax: + 49 (0) 71 61 66-233, www.schulergroup.com.